This invention relates to a system for detecting the occurrence of a misfire in an internal combustion engine.
One of the major causes of air pollution generated by internal combustion engines is the discharge of unburned hydrocarbons which may occur, for example, should one or more of the engine's cylinders misfire. Therefore, it is important in minimizing such air pollution to determine the occurrence of such misfire events.
Prior art systems for detecting misfires in internal combustion engines monitor the speed and acceleration of the engine crankshaft. Misfire events are associated with rapid deceleration. Speed and acceleration are usually determined by accurately measuring the time between subsequent engine control signals (associated with the rotation of the crankshaft). Elaborate software techniques are used to calculate running averages and other statistical properties of the engine dynamics.
Such prior art systems are not wholly satisfactory because they require significant engine controller computer resources. In addition, such systems did not provide adequate results at high RPM rates under low load conditions, especially for engines of eight or more cylinders. In addition, such systems had difficulty differentiating between engine transients resulting from normal vehicle operation and misfire events.